I am downloading a very large torrent (~60GB) and when deluge clients starts up it takes a lot of time to check the parts downloaded during witch it uses a lot the hardisk that leads to a very slow computer.

Is there a way to skip this checking ? or make it be less aggressive on the hardrive ?

The checking is part of the way Bittorrent works. Since the BT protocol treats each chunk separately, the client needs to make sure that every chunk has the proper checksum/hash before it "knows" whether a chunk has been downloaded or not.

Usually it happens pretty seamlessly in the background, but for a 60GB download, the program will have to check every bit of the 60GB set aside on the hard drive to see what's been downloaded and what hasn't been. I don't think there are clients that don't do this check when starting a new session, since I imagine it'd still have to check to make sure nothing's been moved/changed/deleted since the last session

To Shane "I don't think there are clients that don't do this check when starting a new session". Yes, there is: uTorrent. It saves the session, so after a reboot it doesn't have to recheck everything. Having open 400GB of torrents, this is a lifesaver-feature. The main reason why Deluge isn't a good torrentprogram yet.